This must have already been discussed on plenty of other forums, but here I am, I want to use my Graupner FM transmitter / receiver with my quadcopter.

As Jordi from DIY Drones says “Intercept the PPM signal is the best way to obtain all the channels from any receiver, for a lot of reasons. The first one is performance, and the second is the simplicity (in code =P).”

First of all, here’s a quite useful diagram that explains well how the PPM works, and the relationship between this signal and the individual channels: